Among examples of the conventional vehicle hood control apparatus is a pedestrian-protecting sensor system disclosed in Japanese Patent Laid-open Publication No. HEI-11-28994. The disclosed pedestrian-protecting sensor system includes at least one load sensor provided on or near a front bumper, and a vehicle speed sensor. Once the vehicle speed detected by the vehicle speed sensor has exceeded a predetermined speed value and characteristics of the output from the load sensor have met predetermined conditions, i.e. once a collision, against a pedestrian, of the vehicle has been detected while the vehicle is traveling at more than a predetermined speed, a flip-up mechanism is activated to flip up or lift a hood in order to protect the pedestrian through cushioning action of the hood.
The vehicle speed sensor in the disclosed sensor system is of a type that detects the vehicle speed on the basis of rotations of a wheel or wheel axle. Thus, when the vehicle wheels uncontrollably slip due to sudden braking applied by a human operator or driver of the vehicle to urgently avoid a collision with a certain external object (particularly, a pedestrian), the vehicle speed sensor would detect a vehicle speed considerably lower than an actual traveling speed of the vehicle, because the vehicle speed detection in this case is based on the rotations of the wheel or wheel axle. Therefore, controlling the operation of the vehicle hood on the basis of the vehicle speed determined from the rotations of the wheel or wheel axle tends to raise the possibility that the vehicle hood will not be activated properly even when predetermined conditions for activating the hood have been met. Namely, in such a case, the pedestrian-protecting sensor system would not run properly so as to afford sufficient protection of a pedestrian, even when the vehicle has collided with the pedestrian at a relatively high speed and the hood is expected to produce a considerable cushioning or damage-reducing effect.